A conventional dynamic vibration absorber for an optical disk is disclosed in Japanese Unexamined Patent Publication No. 2001-256762 and Japanese Unexamined Patent Publication No. 2001-355670, for example. FIG. 4 is a schematic view showing a simplified constitution of an essential part of the optical disk devices disclosed in Japanese Unexamined Patent Publication No. 2001-256762 and Japanese Unexamined Patent Publication No. 2001-355670.
According to the conventional optical disk device shown in FIG. 4, a spindle motor for rotating a disk, a head for reading information on the disk and the like are mounted on a base chassis 52 and the base chassis 52 is mounted on a main chassis (a case serving as a base) 51 through elastic bodies 53.
Recently, since the number of rotations of the disk has increased, a dynamic vibration absorber needs to be provided in order to avoid vibration generated because of the increased of the number of rotations. In this case, a counterweight 55 for absorbing the vibration generated because of the rotation of the spindle motor is mounted on the base chassis 52 through elastic bodies 54a and 54b. 
Since the conventional dynamic vibration absorber and the optical disk device using it are constituted as described above, when the dynamic vibration absorber is mounted on the base chassis, one to four elastic bodies are needed, depending on a configuration of the dynamic vibration absorber. As a result, the number of parts is increased when the dynamic vibration absorber is mounted, so that a cost is increased.